The present invention relates to a height adjustment mechanism, especially to a height adjustment mechanism for an armrest that have a lever arm disposed between an armrest pad and a lower base and working like a Type-2 (Class two) lever for adjusting height of the armrest by pushing one end of the lever arm.
There are various designs of the armrest height adjustment mechanism. The inventor of the present invention has invented an armrest height adjustment device and obtained U.S. Pat. No. 6,336,680 HEIGHT-ADJUSTMENT MECHANISM FOR ARMREST, as shown in FIG. 10 & FIG. 11. The height adjustment mechanism for an armrest includes a sleeve 10, a tubular member 20, a slider 30, a long plate 40, a fixing plate 50, a guiding plate 60 and a retaining block 70. While adjusting height of the armrest, by pulling up a handle 41 manually, the long plate 40 is moved upwards elastically (the spring 43 is extended simultaneously) so that a projection 45 moves upwards and leans against a projection of the guiding plate 60 and a lower end of the guiding plate 60 moves outwards and leaves original position. Thus the retaining block 70 is released from a locating hole 22, as shown in FIG. 9 and now the slider 30 moves freely inside a sliding slot 21 for adjusting the height. After the armrest being adjusted to a new height, the handle 41 is released so that the long plate 40 turns back to the original position by elasticity of the spring 43 and the projection 45 moves downwards to leave the projection 61 of the guiding plate 60. Thus the retaining block 70 automatically turns back by elasticity of the guiding plate 60 and locks into a new locating hole 22 to finish the height adjustment. However, the pulling-up of the handle 41 mentioned above requires more effort and is inconvenient for the user. Moreover, the handle 41 on a top end of the long plate 40 projecting outwards has negative effects on appearance of the lower base of the armrest.